Providing user authentication

ABSTRACT

In particular embodiments, a computing device accesses a device identifier that is encoded in the hardware of the computing device. The device identifier is used to generate a device key that will uniquely identify the particular computing device. The computing device stores the device key in a data store, and sends the device key to be stored on a first computer server. The computing device subsequently requests a user action from a second computer server, and the second computing server requests user authentication. The computing device generates a first authentication code using a cryptographic hash algorithm and the device key, and sends the first authentication code to the second computer server. The computing device is authenticated based on a second authentication code generated by the first computer server using the device key.

PRIORITY

This application is a continuation under 35 U.S.C. §120 of U.S. patent application Ser. No. 15/233,614, filed 10 Aug. 2016, which is a continuation under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/668,083, filed 2 Nov. 2012, now U.S. Pat. No. 9,444,624.

TECHNICAL FIELD

This disclosure generally relates to user authentication, in particular, user authentication in association with an identified device.

BACKGROUND

A mobile computing device—such as a smartphone, tablet computer, or laptop computer—may include functionality for determining its location, direction, or orientation, such as a GPS receiver, compass, or gyroscope. Such a device may also include functionality for wireless communication, such as BLUETOOTH communication, near-field communication (NFC), or infrared (IR) communication or communication with a wireless local area networks (WLANs) or cellular-telephone network. Such a device may also include one or more cameras, scanners, touchscreens, microphones, or speakers. Mobile computing devices may also execute software applications, such as games, web browsers, or social-networking applications. With social-networking applications, users may connect, communicate, and share information with other users in their social networks.

SUMMARY OF PARTICULAR EMBODIMENTS

In particular embodiments, users associated with a personal computing device can use the personal computing device to authenticate their identity in association with an online system where the user has a user account. A device identifier may be imprinted on to a chip in the personal computing device. The identifier is provided to the online system to be associated with the user account. After that point, whenever the online system requires additional verification of the user's identity, the user can use their personal computing device to generate a code based on the device identifier and enter the code into an interface provided by the online system. The online system can then generate its own comparable code based on the device identifier, and then compare the code entered by the user to the generated code to see if they match. In particular embodiments, a third-party system may also be able to utilize this authentication functionality by requiring the user to enter the code and requesting a generated code from the online system. A disavowal process may also be provided in order to enable the user to disassociate their identity with the device identifier prior to selling, giving away, or otherwise disposing of the personal computing device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B are wireframes showing examples of an interface for provisioning a device identifier.

FIGS. 1C-D are wireframes showing examples of an interface for authenticating a user.

FIG. 2 is a flowchart of an example method according to particular embodiments.

FIGS. 3A-C are interaction diagrams of processes according to particular embodiments.

FIG. 4 is a block diagram of an example network environment.

FIG. 5 is a block diagram of an example computer system.

DESCRIPTION OF PARTICULAR EMBODIMENTS

FIGS. 1A-D are wireframes showing examples of a graphical user interface (GUI) for provisioning a device identifier from personal computing device to an online system and for authentication of a user using a code generated based on the device identifier. In particular embodiments, device 100 includes a display screen 110. In particular embodiments, device 100 may also include a chip imprinted or encoded with a device identifier. The user associated with device 100 may be a member of an online system including a plurality of user accounts, in which a profile for the user may be maintained in association with a user account. The online system may be capable of providing authentication functionality in conjunction with device 100. Device 100 may include software to generate authentication codes based upon the device identifier. Device 100 may also be able to connect to the online system by way of a communications network, such as a cell network or Wi-Fi. Particular embodiments of a network environment associated with an online system as described above are described in further detail in FIG. 5 and related text in the specification. As one of skill in the art would be aware, embodiments of the invention are not limited to the examples described in FIGS. 1A-D and may be performed in association with other types of computing devices as described in FIG. 6 and related text in the specification.

In the example wireframe in FIG. 1A, a user of device 100 has decided to utilize the Authentication Code Generator functionality so as to enable a higher level of security for actions taken with respect to an online system where the user has set up a user account. In order to use this functionality, the user must first associate device 100 with the user's account in the online system. Device 100 displays an interface on display screen 110 with instructions on how to do this. The device identifier 120 shown on display screen 110 may be the device identifier, or it may be a derivative generated by device 100, e.g., a cryptographic hash of the device identifier and the username and password associated with the user's user account.

In the example wireframe in FIG. 1B, a browser screen 150 is illustrated. Browser screen 150 may be displayed on another computing device, e.g., a desktop computer, of the user. Browser screen 150 displays a GUI including entry fields where the user can type in the device identifier once it is displayed on the screen 110 of device 100. In particular embodiments, once the user has entered the device identifier and clicked on the “Activate” button, the online system stores the device identifier in a user profile for the user account. In particular embodiments, no display or entry of the device identifier by the user into a browser may be necessary—all that may be required is to simply click a button or configure a setting in an interface displayed on device 100, at which point device 100 uploads the device identifier to the online system without further input by the user.

In the example wireframe in FIG. 1C, the user is attempting an action requiring heightened security, in this case, a password reset, while using the other computing device, e.g., a desktop computer, of the user. In browser screen 150, the “Reset Password” GUI is requiring the user to generate an authentication code on device 100 and enter the authentication code into entry fields 170. While the user is generating and entering the authentication code, online system uses the device identifier associated with the user to generate its own version of the authentication code, e.g., a hash of the device identifier and a timestamp.

In the example wireframe in FIG. 1D, the user utilizes the Authentication Code Generator program on device 100 to generate an authentication code 130 that is then displayed on screen 110 of device 100. Authentication code 130 is generated based on the device identifier stored on device 100 using the same method used by the online system. Once the user enters authentication code 130 into entry fields 170 and clicks the “Authenticate” button, the online system compares the authentication code it generated with the authentication code entered by the user into entry fields 170. If the two codes match, the user is deemed authenticated. In this manner, the user is afforded extra security against those who might attempt to access the user's account and perform certain actions.

The steps involved in providing authentication functionality based on user association with an identified device, as shown in FIG. 1, are described in further detail in FIG. 2 and related text in the specification.

FIG. 2 is a flowchart of an example method for provisioning a device identifier from personal computing device to an online system and for authentication of a user using a code generated based on the device identifier.

In step 210, a user account for the user is created in the online system. In particular embodiments, the user account may be associated with user profile information. In particular embodiments, the user may begin using a device on which authentication code generating functionality may be available.

In step 220, the online system receives a device key—this device key may be the device identifier, or it may be a derivative generated by the device, e.g., a cryptographic hash of the device identifier and the username and password associated with the user's user account. Any conventional technique for generating such a derivative of the device identifier may be utilized, such as, for example and without limitation, using a cryptographic hash algorithm (e.g., SHA-1, SHA-2, MDS, HAVAL, RadioGatún, RIPEMD-160, SWIFFT, Tiger2, Whirlpool, VSH). This device key may be entered by the user, e.g., by typing it into a GUI provided in a browser or other application or otherwise entering it into a user interface, or sent directly by the device associated with the user. In particular embodiments, the device may first attempt to send the device key directly to the online system and only require the user to enter the device key manually if the device does not have sufficient network connectivity, or if the online system fails to send back an acknowledgment that it was received. In particular embodiments, when the user is entering the device key manually into an interface provided using a browser or other application, the interface may have required the user to enter the authentication code twice as a safeguard against error. In particular embodiments, the online system may require the user to wait until the device has sufficient network connectivity to send the device key directly to the online system.

In step 230, the online system stores the device key in association with the user account of the user for use in future situations requiring additional authentication. The device key may be stored as a part of the user's profile information. In particular embodiments, where the device key is based on the device identifier and also other elements, such as the user's username, password, or other personal information, whenever the user updates one or more of the other elements, the user may be required to re-generate the device key and update the version stored on the online system.

In step 240, the online system receives a request via the user's browser or other application to take an action requiring authentication. In particular embodiments, authentication may be required for such an action by default, or based on a context of the action (e.g., requesting a password reset after multiple recent unsuccessful attempts to log in), or based on configuration settings configured by the user. In particular embodiments, where third-party access is provided for authentication functionality, the request may have been received at a third-party system.

In step 250, the online server displays an interface in the user's browser or other application for the user to enter an authentication code generated by their device, which is based on the device key. In the context of third-party access, either the third-party system may provide the interface for the user to enter the authentication code, or the third-party system may enable display of an interface by the online server (e.g., in a pop-up window or in an iframe). At this point, the device user uses their device to generate an authentication code, and enters it into the interface. In particular embodiments, the authentication code may be a derivative of the device key, such as, for example and without limitation, a cryptographic hash of the device key and a truncated timestamp. In particular embodiments, the interface provided by the online server may enable entry of the authentication code from the device in a more automated fashion, such as scanning an image of a QR code displayed on the screen of the device and captured by a web cam.

In step 260, the online server receives the authentication code entered by the device user using the interface. In particular embodiments, rather than providing an interface for the user to enter the authentication code, the online server may request that the user transmit the authentication code generated by the device to the online server directly from the device if sufficient network connectivity exists for the device. For example, the online server may instruct the user to utilize an interface on the device, which may enable to user to click a button or otherwise indicate that an authentication code should be sent directly to the online server. For example, the user may open an authentication code generator application on the device, from which the user can simply click a button to transmit an authentication code, or, in more secure versions of this interface, in order to transmit the authentication code, the user may be required to enter a password, perform a swipe gesture in a particular pattern, provide biometric identification, etc.

In step 270, the online server generates its own version of the authentication code based on the device key. In particular embodiments, the method used by the online server is the same as the method used by the device to generate its version of the authentication code.

In step 280, the online server compares the authentication code entered by the user with the authentication code generated by the online server. If the two codes match, the user is deemed authenticated. If the two authentication codes fail to match, the user may be asked to generate a new authentication code, and the online server will generate a new authentication code, and the two new authentication codes will be compared. In the example provided above, where the authentication code is based on a hash incorporating a truncated timestamp, this technique enables generation of authentication codes that expire within a set period of time corresponding to the truncated timestamp (e.g., every one minute, or every hour). For this reason, it may be more common that the two authentication codes fail to match—because either the user-generated authentication code or the system-generated authentication code expired prior to comparison.

A disavowal process may also be provided in order to enable the user to disassociate their identity with the device identifier prior to selling, giving away, or otherwise disposing of the computing device. When the user provides an indication that they wish to disavow their association with the computing device, one example of the disavowal process may comprise deleting the device key and any authentication codes based on the device key from the online server, as well as from the computing device itself. In particular embodiments, the user may be required to enter a confirmation of such an action (e.g., by entering their password). In particular embodiments, the user may also “log out” of the computing device and thereby disavow their association with the computing device. In particular embodiments, such a disavowal may be reversible for a predetermined period of time after taking such an action, in order to prevent the scenario where such action was taken in error.

FIG. 3A is an interaction diagram of an example process for associating a device identifier encoded in a computing device 500 with a user account in an online system 430. As a first step, a user account is created 310 in the online system for a user of computing device 500. Either upon initial setup, login, activation of the authentication functionality, or any other logical occasion, computing device 500 will be required to provide a device key. Computing device 500 may then retrieve a hardware-encoded device identifier 312—the device key provided by computing device 500 may be the device identifier itself, or it may be a derivative thereof. Computing device 500 then provides the device key to online system 430 to be associated with the user account 314. This may be accomplished either by automatic upload by computing device 500, or by manual entry by the user into a browser or other application interface. Online system 430 then stores the device key in association with the user account 316, possibly as part of a set of user profile information maintained for the user account. Once these steps are complete, computing device 500 is deemed to be associated with the user account and thereby provisioned to the online system for use in authentication procedures.

FIG. 3B is an interaction diagram of an example process for authentication of a user using authentication codes generated based on the device identifier. Once computing device 500 has been provisioned to online system 430, online system 430 may receive a request requiring authentication 350, such as, for example and without limitation, a password reset, an update of a username or password associated with the user account, an update of a credit card number or other financial information, an update of a social security number or driver's license number or other uniquely-identifying information, a purchase, a registration, or any other action deemed to require authentication. Online system 430 may then display an interface 352 in a browser or other application for the user to enter an authentication code generated by computing device 500. At this point, the user may access the authentication code generator functionality on computing device 500 to request an authentication code 354. Computing device 500 generates an authentication code 356 and displays or otherwise provides it to the user so that the user can enter it into the interface. Once online system 430 receives the authentication code 358 entered by the user, or, alternatively, while online system 430 is waiting to receive the authentication code entered by the user, online system 430 generates its own version of the authentication code 360 based on the device key stored in the online system in association with the user account. Online system 360 then compares 362 the authentication code entered by the user with the authentication code generated by the online system 360 in order to determine whether the user can be deemed authenticated.

FIG. 3C is an interaction diagram of an example process for authentication of a user by a third-party system using authentication codes generated based on the device identifier. Third-party system 440 may receive a request requiring authentication 370. Third-party system 440 may then send a request 372 to online system 430 for an authentication code generated by online system 430. The request may include an identifier for the user, such as, for example and without limitation, a userID, an email address, a phone number, etc. Third-party system 440 may also display an interface 374 in a browser or other application for the user to enter an authentication code generated by computing device 500. This interface may be provided by third-party system 440, or third-party system 440 may enable display of an interface provided by online system 430 (e.g., using a pop-up window or an iframe).

In the meantime, online system 430 generates its own version of the authentication code 376 based on the device key stored in the online system in association with the user account. At this point, the user may access the authentication code generator functionality on computing device 500 to generate an authentication code 378 and enter it into the interface. Once online system 430 provides its generated authentication code 380 to third-party system 440, and third-party system 440 receives then authentication code entered by the user 382, third-party system 440 then compares 384 the user-entered authentication code with the system-generated authentication code in order to determine whether the user can be deemed authenticated.

In particular embodiments, an application programming interface (API) or other third-party interface may be provided in order to enable third-party system 440 to access the authentication functionality.

FIG. 4 illustrates an example network environment 400. Network environment 400 may include a user 410, a client system 500, an online system 430, and a third-party system 440 connected to each other by a network 450. Although FIG. 4 illustrates a particular arrangement of user 410, client system 500, online system 430, third-party system 440, and network 450, this disclosure contemplates any suitable arrangement of user 410, client system 500, online system 430, third-party system 440, and network 450. As an example and not by way of limitation, two or more of client system 500, online system 430, and third-party system 440 may be connected to each other directly, bypassing network 450. As another example, two or more of client system 500, online system 430, and third-party system 440 may be physically or logically co-located with each other in whole or in part. Moreover, although FIG. 4 illustrates a particular number of users 410, client systems 500, online systems 430, third-party systems 440, and networks 450, this disclosure contemplates any suitable number of users 410, client systems 500, online systems 430, third-party systems 440, and networks 450. As an example and not by way of limitation, network environment 400 may include multiple users 410, client system 500, online systems 430, third-party systems 440, and networks 450.

In particular embodiments, user 410 may be an individual (human user), an entity (e.g., an enterprise, business, or third-party application), or a group (e.g., of individuals or entities) that interacts or communicates with or over online system 430. In particular embodiments, online system 430 may be a network-addressable computing system hosting applications. Online system 430 may generate, store, receive, and transmit user-associated data, such as, for example, user-profile data, concept-profile data, social-graph information, or other suitable data related to the online system. Online system 430 may be accessed by the other components of network environment 400 either directly or via network 450. In particular embodiments, online system 430 may include an authorization server that allows users 410 to opt in or opt out of having their actions logged by online system 430 or shared with other systems (e.g., third-party systems 440), such as, for example, by setting appropriate privacy settings. In particular embodiments, third-party system 440 may be a network-addressable computing system that can host third-party content objects and serve content, and/or provide a third-party advertisement serving engine.. Third-party system 440 may generate, store, receive, and transmit third-party content and/or sponsored content, such as, for example, advertisements, incentive program notifications, coupons, etc. Third-party system 440 may be accessed by the other components of network environment 400 either directly or via network 450. In particular embodiments, one or more users 410 may use one or more client systems 500 to access, send data to, and receive data from online system 430 or third-party system 440. Client system 500 may access online system 430 or third-party system 440 directly, via network 450, or via a third-party system. As an example and not by way of limitation, client system 500 may access third-party system 440 via online system 430. Client system 500 may be any suitable computing device, such as, for example, a personal computer, a laptop computer, a cellular telephone, a smartphone, or a tablet computer.

This disclosure contemplates any suitable network 450. As an example and not by way of limitation, one or more portions of network 450 may include an ad hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan area network (MAN), a portion of the Internet, a portion of the Public Switched Telephone Network (PSTN), a cellular telephone network, or a combination of two or more of these. Network 450 may include one or more networks 450.

Links 460 may connect client system 500, online system 430, and third-party system 440 to communication network 450 or to each other. This disclosure contemplates any suitable links 460. In particular embodiments, one or more links 460 include one or more wireline (such as for example Digital Subscriber Line (DSL) or Data Over Cable Service Interface Specification (DOC SIS)), wireless (such as for example Wi-Fi or Worldwide Interoperability for Microwave Access (WiMAX)), or optical (such as for example Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH)) links. In particular embodiments, one or more links 460 each include an ad hoc network, an intranet, an extranet, a VPN, a LAN, a WLAN, a WAN, a WWAN, a MAN, a portion of the Internet, a portion of the PSTN, a cellular technology-based network, a satellite communications technology-based network, another link 460, or a combination of two or more such links 460. Links 460 need not necessarily be the same throughout network environment 400. One or more first links 460 may differ in one or more respects from one or more second links 460.

FIG. 5 illustrates an example computer system 500. In particular embodiments, one or more computer systems 500 perform one or more steps of one or more methods described or illustrated herein. In particular embodiments, one or more computer systems 500 provide functionality described or illustrated herein. In particular embodiments, software running on one or more computer systems 500 performs one or more steps of one or more methods described or illustrated herein or provides functionality described or illustrated herein. Particular embodiments include one or more portions of one or more computer systems 500. Herein, reference to a computer system may encompass a computing device, where appropriate. Moreover, reference to a computer system may encompass one or more computer systems, where appropriate.

This disclosure contemplates any suitable number of computer systems 500. This disclosure contemplates computer system 500 taking any suitable physical form. As example and not by way of limitation, computer system 500 may be an embedded computer system, a system-on-chip (SOC), a single-board computer system (SBC) (such as, for example, a computer-on-module (COM) or system-on-module (SOM)), a desktop computer system, a laptop or notebook computer system, an interactive kiosk, a mainframe, a mesh of computer systems, a mobile telephone, a personal digital assistant (PDA), a server, a tablet computer system, another mobile computing device, or a combination of two or more of these. Where appropriate, computer system 500 may include one or more computer systems 500; be unitary or distributed; span multiple locations; span multiple machines; span multiple data centers; or reside in a cloud, which may include one or more cloud components in one or more networks. Where appropriate, one or more computer systems 500 may perform without substantial spatial or temporal limitation one or more steps of one or more methods described or illustrated herein. As an example and not by way of limitation, one or more computer systems 500 may perform in real time or in batch mode one or more steps of one or more methods described or illustrated herein. One or more computer systems 500 may perform at different times or at different locations one or more steps of one or more methods described or illustrated herein, where appropriate.

In particular embodiments, computer system 500 includes a processor 502, memory 504, storage 506, an input/output (I/O) interface 508, a communication interface 510, and a bus 512. Although this disclosure describes and illustrates a particular computer system having a particular number of particular components in a particular arrangement, this disclosure contemplates any suitable computer system having any suitable number of any suitable components in any suitable arrangement.

In particular embodiments, processor 502 includes hardware for executing instructions, such as those making up a computer program. As an example and not by way of limitation, to execute instructions, processor 502 may retrieve (or fetch) the instructions from an internal register, an internal cache, memory 504, or storage 506; decode and execute them; and then write one or more results to an internal register, an internal cache, memory 504, or storage 506. In particular embodiments, processor 502 may include one or more internal caches for data, instructions, or addresses. This disclosure contemplates processor 502 including any suitable number of any suitable internal caches, where appropriate. As an example and not by way of limitation, processor 502 may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory 504 or storage 506, and the instruction caches may speed up retrieval of those instructions by processor 502. Data in the data caches may be copies of data in memory 504 or storage 506 for instructions executing at processor 502 to operate on; the results of previous instructions executed at processor 502 for access by subsequent instructions executing at processor 502 or for writing to memory 504 or storage 506; or other suitable data. The data caches may speed up read or write operations by processor 502. The TLBs may speed up virtual-address translation for processor 502. In particular embodiments, processor 502 may include one or more internal registers for data, instructions, or addresses. This disclosure contemplates processor 502 including any suitable number of any suitable internal registers, where appropriate. Where appropriate, processor 502 may include one or more arithmetic logic units (ALUs); be a multi-core processor; or include one or more processors 502. Although this disclosure describes and illustrates a particular processor, this disclosure contemplates any suitable processor.

In particular embodiments, memory 504 includes main memory for storing instructions for processor 502 to execute or data for processor 502 to operate on. As an example and not by way of limitation, computer system 500 may load instructions from storage 506 or another source (such as, for example, another computer system 500) to memory 504. Processor 502 may then load the instructions from memory 504 to an internal register or internal cache. To execute the instructions, processor 502 may retrieve the instructions from the internal register or internal cache and decode them. During or after execution of the instructions, processor 502 may write one or more results (which may be intermediate or final results) to the internal register or internal cache. Processor 502 may then write one or more of those results to memory 504. In particular embodiments, processor 502 executes only instructions in one or more internal registers or internal caches or in memory 504 (as opposed to storage 506 or elsewhere) and operates only on data in one or more internal registers or internal caches or in memory 504 (as opposed to storage 506 or elsewhere). One or more memory buses (which may each include an address bus and a data bus) may couple processor 502 to memory 504. Bus 512 may include one or more memory buses, as described below. In particular embodiments, one or more memory management units (MMUs) reside between processor 502 and memory 504 and facilitate accesses to memory 504 requested by processor 502. In particular embodiments, memory 504 includes random access memory (RAM). This RAM may be volatile memory, where appropriate Where appropriate, this RAM may be dynamic RAM (DRAM) or static RAM (SRAM). Moreover, where appropriate, this RAM may be single-ported or multi-ported RAM. This disclosure contemplates any suitable RAM. Memory 504 may include one or more memories 504, where appropriate. Although this disclosure describes and illustrates particular memory, this disclosure contemplates any suitable memory.

In particular embodiments, storage 506 includes mass storage for data or instructions. As an example and not by way of limitation, storage 506 may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage 506 may include removable or non-removable (or fixed) media, where appropriate. Storage 506 may be internal or external to computer system 500, where appropriate. In particular embodiments, storage 506 is non-volatile, solid-state memory. In particular embodiments, storage 506 includes read-only memory (ROM). Where appropriate, this ROM may be mask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. This disclosure contemplates mass storage 506 taking any suitable physical form. Storage 506 may include one or more storage control units facilitating communication between processor 502 and storage 506, where appropriate. Where appropriate, storage 506 may include one or more storages 506. Although this disclosure describes and illustrates particular storage, this disclosure contemplates any suitable storage.

In particular embodiments, I/O interface 508 includes hardware, software, or both providing one or more interfaces for communication between computer system 500 and one or more I/O devices. Computer system 500 may include one or more of these I/O devices, where appropriate. One or more of these I/O devices may enable communication between a person and computer system 500. As an example and not by way of limitation, an I/O device may include a keyboard, keypad, microphone, monitor, mouse, printer, scanner, speaker, still camera, stylus, tablet, touch screen, trackball, video camera, another suitable I/O device or a combination of two or more of these. An I/O device may include one or more sensors. This disclosure contemplates any suitable I/O devices and any suitable I/O interfaces 508 for them. Where appropriate, I/O interface 508 may include one or more device or software drivers enabling processor 502 to drive one or more of these I/O devices. I/O interface 508 may include one or more I/O interfaces 508, where appropriate. Although this disclosure describes and illustrates a particular I/O interface, this disclosure contemplates any suitable I/O interface.

In particular embodiments, communication interface 510 includes hardware, software, or both providing one or more interfaces for communication (such as, for example, packet-based communication) between computer system 500 and one or more other computer systems 500 or one or more networks. As an example and not by way of limitation, communication interface 510 may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI network. This disclosure contemplates any suitable network and any suitable communication interface 510 for it. As an example and not by way of limitation, computer system 500 may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, computer system 500 may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination of two or more of these. Computer system 500 may include any suitable communication interface 510 for any of these networks, where appropriate. Communication interface 510 may include one or more communication interfaces 510, where appropriate. Although this disclosure describes and illustrates a particular communication interface, this disclosure contemplates any suitable communication interface.

In particular embodiments, bus 512 includes hardware, software, or both coupling components of computer system 500 to each other. As an example and not by way of limitation, bus 512 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination of two or more of these. Bus 512 may include one or more buses 512, where appropriate. Although this disclosure describes and illustrates a particular bus, this disclosure contemplates any suitable bus or interconnect.

Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such, as for example, field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. 

What is claimed is:
 1. A method comprising: by a first computing device, receiving a request to associate a client system to a user account of an online system, wherein the request comprises a device key that uniquely identifies the client system, wherein the device key is based on a device identifier encoded in hardware of the client system; by the first computing device, storing the device key in a user profile for the user account; by the first computing device, receiving, from a second computing device, a request for an authentication code for the user account; by the first computing device, generating a first authentication code using a first cryptographic hash algorithm executed based on the device key; and by the first computing device, sending, to the second computing device, the first authentication code, wherein the second computing device authenticates the user by comparing the first authentication code with a second authentication code received from one of client devices associated with the user account, wherein the second authentication code was generated by the client system using a second cryptographic hash algorithm executed based on the device key.
 2. The method of claim 1, wherein the first computing device is a part of the online system, wherein the online system maintains the user profile for the user account in a data store.
 3. The method of claim 1, wherein the device key is further based on: a username of the user account associated with the client computing device; a password of the user account; or other personal information associated with the user account.
 4. The method of claim 3, further comprising: receiving a request to update the device key from one of client devices associated with the user account, wherein the update is triggered by an update of the username, the password, or other personal information of the user; and updating the device key of the client computing device in response to the update.
 5. The method of claim 1, wherein the client system comprises software generating authentication codes based on the device key using the second cryptographic hash algorithm.
 6. The method of claim 1, wherein the second computing device is associated with a third-party system that relies on the online system for authenticating the user account.
 7. The method of claim 1, wherein the second computing device is a part of the online system and processes user requests requiring heightened security.
 8. The method of claim 1, wherein the first cryptographic hash algorithm and the second cryptographic hash algorithm are identical algorithms.
 9. The method of claim 1, wherein the generating the first authentication code is further based on a timestamp.
 10. The method of claim 1, further comprising: receiving a disavowal request from one of client devices associated with the user account; and deleting the device key stored on the data store of the client computing device.
 11. The method of claim 10, wherein the deletion is reversible for a predetermined period of time.
 12. One or more computer-readable non-transitory storage media embodying software that is operable when executed to: receive a request to associate a client system to a user account of an online system, wherein the request comprises a device key that uniquely identifies the client system, wherein the device key is based on a device identifier encoded in hardware of the client system; store the device key in a user profile for the user account; receive, from a second computing device, a request for an authentication code for the user account; generate a first authentication code using a first cryptographic hash algorithm executed based on the device key; and send, to the second computing device, the first authentication code, wherein the second computing device authenticates the user by comparing the first authentication code with a second authentication code received from one of client devices associated with the user account, wherein the second authentication code was generated by the client system using a second cryptographic hash algorithm executed based on the device key.
 13. The media of claim 12, wherein the device key is further based on: a username of the user account associated with the client computing device; a password of the user account; or other personal information associated with the user account.
 14. The media of claim 12, wherein the software is further operable when executed to: receive a request to update the device key from one of client devices associated with the user account, wherein the update is triggered by an update of the username, the password, or other personal information of the user; and update the device key of the client computing device in response to the update.
 15. The media of claim 12, wherein the client system comprises software generating authentication codes based on the device key using the second cryptographic hash algorithm.
 16. The media of claim 12, wherein the second computing device is associated with a third-party system that relies on the online system for authenticating the user account.
 17. The media of claim 12, wherein the second computing device is a part of the online system and processes user requests requiring heightened security.
 18. The media of claim 12, wherein the first cryptographic hash algorithm and the second cryptographic hash algorithm are identical algorithms.
 19. The media of claim 12, wherein the generating the first authentication code is further based on a timestamp.
 20. A system comprising: one or more processors; and a memory coupled to the processors comprising instructions executable by the processors, the processors operable when executing the instructions to: receive a request to associate a client system to a user account of an online system, wherein the request comprises a device key that uniquely identifies the client system, wherein the device key is based on a device identifier encoded in hardware of the client system; store the device key in a user profile for the user account; receive, from a second computing device, a request for an authentication code for the user account; generate a first authentication code using a first cryptographic hash algorithm executed based on the device key; and send, to the second computing device, the first authentication code, wherein the second computing device authenticates the user by comparing the first authentication code with a second authentication code received from one of client devices associated with the user account, wherein the second authentication code was generated by the client system using a second cryptographic hash algorithm executed based on the device key. 